Common Problems And Solutions In The Production Process Of PVC Foam Board

FIRST

In terms of lubricant balance, there is insufficient external sliding, which makes it difficult to control the temperature in zone 5 of the extruder and prone to temperature rise, resulting in high temperature of the merging core, large bubbles, series bubbles, yellowing and other problems in the middle of the board, and the surface of the board is not smooth; Excessive outward sliding can lead to severe precipitation, manifested in the structure inside the mold and the outward sliding of the plate surface, as well as occasional back and forth movement of certain individual phenomena on the plate surface. 2. The manifestation of insufficient internal sliding is that the thickness of the board surface is difficult to control, manifested as thick in the middle and thin on both sides of the board; Excessive internal sliding can lead to high temperatures in the merging core.

SECOND

Regarding the surface of the board, if the extrusion temperature is too high or the stability of the stabilizer is insufficient, the solution is to lower the processing temperature. If there is no improvement, the formula can be adjusted by increasing the amount of stabilizer and lubricant added appropriately. This can be changed one by one, making it easy to quickly identify the problem and solve it as quickly as possible. 2. Yellowing in the middle of the board: The main reason is related to the high temperature of the cylinder area and mold, as well as the amount of lubricant used, which is also related to the white hair foaming agent. By adjusting the process temperature or adjusting the proportion of white hair bubbles added for processing. 3. Bending of the board surface: The main reason for uneven material flow or inadequate cooling is generally due to factors such as large traction fluctuations or uneven internal and external lubrication in the formula. Machine factors are easily eliminated, and formula adjustment is generally based on minimizing external lubrication while adjusting internal lubrication to achieve good results, while ensuring uniform cooling. During the production process, the water temperature of the mold is generally controlled at 30-40 ℃, and the optimal range for the shaping table water temperature is generally controlled at 15-20 ℃. 4. Uneven board thickness: Uneven discharge. The height of the mold lip can be adjusted. If the flow rate is too high, the blocking rod can be adjusted, and the formula can be adjusted. Generally, if there is more internal lubrication in the middle, it will be thicker, and if there is more external lubrication, the material will flow faster on both sides. 5. The changes in thickness, texture, and other characteristics of the board that are prone to occur during shift handover are mainly due to fluctuations in the mixing materials. After mixing in the previous shift, the interval between mixing in the next shift is long, and the hot mixing pot is well cooled. The first batch of mixed materials is pre plasticized, which is different from the previous mixing. Under other unchanged conditions, fluctuations are prone to occur. This can be solved by adjusting the traction and processing temperature or by standardizing the mixing handover process.

THIRD

In terms of foam section bubbles, the reason for the appearance of bubbles or bubble delamination in the transverse section can be attributed to one point, which is insufficient melt strength. The reasons for insufficient melt strength are: firstly, excessive foaming agent or insufficient foaming regulator, or the ratio of the two is not coordinated, or the quality of foaming regulator is a problem. The second is poor plasticization, low processing temperature or excessive lubrication. 2. There are two factors that contribute to the formation of bubbles or penetration in the cross-section of foam plastic sheets: firstly, the local strength of the melt itself is too low, and the bubbles are formed from the outside to the inside; The second reason is that the pressure around the melt is relatively low, causing local bubbles to expand and weaken in strength. The bursting of bubbles is formed from the inside out. In production practice, there is no significant difference between the two functions, and they may exist simultaneously. Most of the broken holes are caused by uneven expansion of local bubbles, resulting in a decrease in melt strength.